Review of ABO Expression and Variations based on Transcriptional Regulation of the ABO Blood Group Gene

Serological and genetic analysis of a B3 phenotype caused by c.259G > T in the ABO gene

BACKGROUND

Mixed agglutination is a serological pattern in some ambiguous ABO blood type identification. This study focused on the serological and molecular genetic characteristics of a B3 phenotype induced by a c.259G > T mutation in the ABO gene.

STUDY DESIGN AND METHODS

Serological methods such as gel cards and tubes were used to identify the ABO blood type of the patient, with fluorescent PCR for ABO genotyping and Sanger sequencing for analysing the ABO exons. Protein 3D Structure was simulated and further analysed using SWISS-MODLE and PyMOL. Both the wild-type (VAL-87, ABO*B.01) and the mutant (p.Val87Leu) plasmids were transfected into Hela cells to assess the agglutination intensity of the transfected cells with anti-B antibodies.

RESULTS

Serological testing showed weak expression of the B antigen and mixed agglutination with anti-B antibodies. ABO genotyping indicated the presence of a B allele, but exon sequencing revealed an additional c.259G > T mutation in exon 6 based on the ABO*B.01 allele. The simulated three-dimensional structures of the proteins showed increased steric hindrance with mutations, leading to a relatively loose structure. The transfected Hela cells with the mutant (p.Val87Leu) plasmid exhibited a significantly reduced agglutination intensity with anti-B antibodies.

CONCLUSION

Based on comprehensive serological, genetic, and simulation analyses, it is concluded that the c.259G > T mutation in exon 6 of the ABO*B.01 allele results in an amino acid change within the enzymatic active site. This alteration likely impacts protein stability and reduces B antigen expression, leading to the B3 subtype phenotype.

Identification of an AweakB phenotype caused by significant ABO gene deletion in a Chinese woman

BACKGROUND AND OBJECTIVES

The AweakB is a rare phenotype in the ABO blood group system. Here, we first report a novel ABO mutation discovered in a Chinese woman with an AweakB. Third-generation sequencing was employed to investigate the molecular mechanisms underlying AweakB. By correctly identifying the phenotype, it was useful for increasing the safety of blood transfusion.

MATERIALS AND METHODS

ABO blood group was identified by the standard ABO serological test and polymerase chain reaction with sequence-specific primers (PCR-SSP). To analyse the ABO gene sequence, single-molecule real-time (SMRT) sequencing was performed to obtain full-length sequencing of the ABO gene.

RESULTS

The Chinese individual was serologically identified as AweakB subtype, and SMRT sequencing analysis revealed that there were large fragment deletion mutations in the promoter (c.1-1326_1-1321del, c.1-1010_1-975del, c.1-952_1-1del) and Exon 1 region (c.1_28del).

CONCLUSION

We report for the first time that large fragment deletions represent a novel molecular basis for the AweakB. These deletions may potentially influence the expression of the A antigen.